Fix SF bug #667147, Segmentation fault printing str subclass

Fix infinite recursion which occurred when printing an object
whose __str__() returned self.

Will backport

1 files changed, 24 insertions, 1 deletions

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 023fcc8..da4bd03 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1,6 +1,6 @@
 # Test enhancements related to descriptors and new-style classes
 
-from test.test_support import verify, vereq, verbose, TestFailed, TESTFN
+from test.test_support import verify, vereq, verbose, TestFailed, TESTFN, get_original_stdout
 from copy import deepcopy
 import warnings
 
@@ -1821,6 +1821,29 @@ def specials():
     unsafecmp(1, 1L)
     unsafecmp(1L, 1)
 
+    class Letter(str):
+        def __new__(cls, letter):
+            if letter == 'EPS':
+                return str.__new__(cls)
+            return str.__new__(cls, letter)
+        def __str__(self):
+            if not self:
+                return 'EPS'
+            return self 
+
+    # sys.stdout needs to be the original to trigger the recursion bug
+    import sys
+    test_stdout = sys.stdout
+    sys.stdout = get_original_stdout()
+    try:
+        # nothing should actually be printed, this should raise an exception
+        print Letter('w')
+    except RuntimeError:
+        pass
+    else:
+        raise TestFailed, "expected a RuntimeError for print recursion"
+    sys.stdout = test_stdout
+
 def weakrefs():
     if verbose: print "Testing weak references..."
     import weakref